Backpack



FIG. 1 is a front view of a backpack embodying the new design;

FIG. 2 is a right-side perspective view thereof;

FIG. 3 is a top and right side perspective view thereof;

FIG. 4 is a left-side perspective view thereof;

FIG. 5 is a rear view thereof with removable chest and hip straps; and,

FIG. 6 is a rear view thereof without the removable chest and hip straps.

The broken line showing of portions of the backpack is for the purpose of illustrating stitching and forms no part of the claimed design. 

CLAIM The ornamental design for a backpack, as shown and described. 